1. Field of the Invention
The present invention relates to band-saws which are intended to be employed for sawing metal parts such as bars or the like.
2. Description of the Prior Art
Machines of this type which correspond to the best current technique are the so-called "horizontal band-saws". In a typical machine, a work unit is capable of displacement in the vertical direction above the table which supports the workpiece to be sawn. This moving unit has two separate and distinct lateral portions which are located on each side of two vertical guiding members and serve as supports for two vertical saw-blade driving and guiding wheels. Since the saw-blade is an endless strip, it has two horizontal runs extending between said wheels, and one of these runs constitutes the work run of the saw-blade.
In current machines of this type, the vertical members for guiding the moving work unit consist of two columns, the lower end of each column being fixed on the work table. The frame of the moving work unit is fitted with sleeves which are slidably mounted on said columns. However, the two side portions of the moving unit are coupled together only at the top in order to leave a free space which is sufficient to permit engagement of the workpiece as said moving unit moves downwards.
This accordingly constitutes a serious drawback since the frame of the work unit is subjected to high compressive stresses in the horizontal direction, these stresses being produced by the high tension of the saw-blade (between 2 and 6 tons according to the cross-sectional area of the blade). These stresses therefore tend to cause deformation of the frame of the work unit and this deformation is sustained by the bearings of the vertical guiding columns.
In point of fact, the guiding columns are mounted "up in the air" since they are fixed on the corresponding table only at their lower ends. Moreover, the guiding zones of the moving work unit are located above the position of the work run of the saw-blade.
These disadvantages can be overcome only by providing a very rigid construction in order to guard against any danger of deformation of the moving work unit and of the vertical guiding columns, thus calling for extremely heavy parts and very accurate machining. This accordingly results in particularly high cost of machines of this type.
Furthermore, these machines are attended by a certain number of disadvantages which also result from their present design. These disadvantages are as follows:
a) In the event that provision is made for a single hydraulic jack for controlling the vertical displacements of the work unit, said jack must necessarily be displaced with respect to the axis of symmetry of said unit in order to ensure that the location provided for workpieces is left free. Such an arrangement is therefore unbalanced. As to the arrangement which consists in providing two control jacks placed on each side, this is clearly more costly.
b) It is necessary to carry out efficient lubrication of the bearings of the guiding columns in order to obtain good operation.
c) The guides of the clamping vise are placed in the swarf and cutting lubricant by reason of the fact that these guides are mounted on the receiving table located beneath the work run of the saw-blade.
d) By reason of the bulk of the moving unit which is located above the work run of the saw-blade, it is difficult to contemplate the addition of a vertical clamping system for cutting bundles of bars.
For the reasons given above, the present invention is directed to a horizontal band-saw which is of different design so as to permit a construction of much lighter weight and therefore less costly and to remove the various other disadvantages recalled in the foregoing.